A typical remotely installed and centrally monitored security device such as a fire protection sensor is commonly connected to a more centralized processing node, such as an alarm system control panel. Detection of an event (such as presence of particulates or ionized gases in air, excessive heat, interruption of a security link, and the like) by the security device is analyzed by the alarm system control panel or other security node. A decision to send out emergency notification such as alarm tones, flashing lights, or telephone calls to emergency responders is then made by an apparatus at the alarm system control panel or, if a hierarchy of control panels is used, at a more central location, based on detecting an unambiguous signal from at least one of a possible plurality of such sensors, and decided in accordance with a procedure encoded in the system.
In systems wherein the number of sensors is large, it is known in the art to connect several sensors in at least one “daisy chain” string according to any of a variety of configurations. In some systems, if at least one of the sensors in the at least one string is subsequently activated, i.e., detects an event, the alarm response can be made, irrespective of a capability by the central apparatus of identifying the exact location in the string of the activated device. In other systems, known methods can permit at least relative location of an activated sensor to be identified, such as by assigning unique identifiers to all sensors and configuring the sensors to transmit these identifiers as part of subsequent alarm messages. Since an alarm response of clearing a building, for example, is likely to be the same for whichever of a plurality of fire sensors in a system limited to that building is activated, the total amount of wiring may be reduced by configurations such as those described above without introducing appreciable risk. Provided adequate testing is regularly performed, such approaches may be broadly adequate within limits.
For some systems, such as those installed in trespass-sensitive environments or in extremely large or multi-building alarm system configurations, provision of a plurality of detection strings may be desirable to improve localization. Similarly, where testing may suggest that one of a large number of sensors on a string is faulty or is located proximal to a wiring damage incident, localization can become an issue. Moreover, initial installation and modification of systems using known apparatus may demand meticulous—and costly—attention to detail and may nonetheless yield ambiguous test results.
In systems using multiple sensors, power consumption within individual sensors, while small, can cumulatively become a limiting factor. In addition to power limitations, signaling trustworthiness of individual sensors of known types back to an alarm system control panel, both during initialization and during an event, can be limited by loading, noise, and related issues.
There are existing methods and apparatus that support, to at least some extent, periodic test and troubleshooting, while maintaining substantially complete functionality. However, many of these existing approaches have been shown to be limited in some applications regarding ease of installation, expandability, verification, and other considerations.
Standards for safety in systems involving life and property are controlled in most countries, using combinations of government agencies, insurance underwriters, and industry practices. In the United States, for example, local building codes typically refer to practices stipulated by the National Fire Protection Association (NFPA) and to Underwriters Laboratories® documents such as UL 864 and associated standards to identify approved components and to restrict practices to those validated by rigorous testing.
Since many existing fire alarm and related systems require maintenance, upgrading, and expansion, introduction of new apparatus incompatible with existing systems can result in market resistance. Even if the concepts motivating the new apparatus are otherwise desirable, incompatibility may deter end users from adopting the enhanced protection of successor devices.
Accordingly, there is a need in the art for an alarm system sensor topology that simplifies installation, reduces troubleshooting time and effort, increases immunity to at least some fault conditions, reduces power consumption, and extends expandability. It is further desirable that such a topology include compatibility with existing systems at least to the extent of permitting prior and successor components to be intermixed in a single system without penalty, and still further desirable that the intermixture of components provide potential for operational enhancement to a system wherein the successor components are installed.